Process for using ester plasticized polyurethanes for sealing electrical devices

ABSTRACT

A plasticized polyurethane gel system comprising the reaction product of an isocyanate compound and a polyol in the presence of an ester plasticizer compound having a total solubility parameter of between about 8.3 and 8.9 or between about 9.1 and 9.7. Said polyurethane systems are cured, cross-linked, non-spewing, grease compatible, and reenterable. This extended polyurethane is further characterized as having superior insulating properties so that it can be used of repairing, encapsulating or reclaiming electrical or telecommunication cables as well as for hard volume encapsulants or general elastomer use.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a division of application Ser. No. 837,554, filedMar. 3, 1986, now U.S. Pat. No. 4,666,968, which is acontinuation-in-part of application Ser. No. 713,377, filed Mar. 19,1985, now abandoned.

TECHNICAL FIELD

The invention relates to polyurethane gels which contain novelplasticizers and which may be formulated as a grease-compatible,non-spewing material for use in reclaiming, encapsulating or sealingelectrical cables or devices.

BACKGROUND ART

It is well-known in the art to extend polymers such as polyurethanes.This extended material will then be designated for use in a desired areaof utility. Typical of such extending agents is mineral oil, suchmineral oil extended polyurethanes being disclosed in U.S. Pat. Nos.3,714,110 and 3,747,037.

It has also been determined that the mineral oil extended polyurethaneis useful in the reclamation and protection of insulated electricaldevices. Such devices may, for example, be underground telephone cableswhich are exposed to fluid contaminants. These contaminants canseriously impair the electrical and mechanical properties of such adevice. The protectant material is pumped into the cable to remove waterthat has penetrated into interior free spaces. The material is pumped atlow viscosity to achieve an appropriate distribution and it then curesin place to a high viscosity. The cured material acts as a hydrophobicbarrier to subsequent water penetration. In another application, thismaterial may be utilized as an encapsulant for sealing sections ofcable. In this manner, the material serves to prevent the penetration offluid contaminants from the outset.

A mineral oil extended polyurethane which is useful for this purpose isdisclosed in U.S. Pat. No. Re. 30,321. That patent defines a cured,cross-linked, mineral oil extended polyurethane prepared from specificpolyurethanes and coupling agents, the latter being necessary tocompatibilize the mineral oil with the cross-linking urethane elastomer.

Disadvantages of these mineral oil extended polyurethane systems wereencountered, however, and these are described in U.S. Pat. No.4,168,258. There it was stated that, with the earlier mineral oilextended polyurethanes, the mineral oil would tend to migrate toward anygrease present in the cable or device in order to be reclaimed orencapsulated. This grease is encountered more frequently in newerinsulated electrical devices. This migration was shown to cause theformation of an oily film at the grease interface which tended todecrease the reclamation and encapsulant effectiveness of thepolyurethane. In order to avoid these difficulties, the patentspecifically defined a polyurethane-mineral oil-coupling agentformulation relying on the presence of a polydiene moiety in thepolyurethane structure. Mineral oil remained as the extending agent,with the stated preference for including some aromatic carbon contenttherein.

It is also known that previous polyurethane compositions have beendifficult to re-enter after they have fully cured primarily due to theirhigh cast strength or aging hardness, as well as due to their opaque orcloudy color. The high cast strength and hardness of these prior artpolyurethanes contribute to the difficulty of cutting through orremoving cured material from a repaired area. In some applications, theopaque color makes it difficult for the operator to establish the exactlocation to reenter a repair, and thus, clear soft polyurethane gels arepreferred.

With either the clear or opaque products, the ability of thesepolyurethanes to be easily reentered is important in the repair orencapsulation of insulated electrical or telephone cables when a secondsplice or connection must be made in the same area as the previousrepair or encapsulation. There are also situations where the initialrepair or encapsulation is improperly made and has to be re-done. Forthese reasons, the primary concern regarding the physical properties ofthese gels is to provide a polyurethane having a relatively low tearstrength and hardness. Furthermore, it is highly desirable for thesematerials to maintain these properties over time.

A vegetable oil extended polyurethane which satisfies some of theserequirements and provides an initially reenterable gel is disclosed inU.S. Pat. No. 4,375,521. There, vegetable oil extended polyurethanes ofa three component system comprising a specific polyurethane, vegetableoil, and specific extending agent is disclosed for use in reclamationand encapsulation applications. However, these vegetable oil extendedformulations usually provide opaque gels, and, more importantly, tend tocause cracking or stressing of the polycarbonate connectors which areusually present in the cable unit being reclaimed, encapsulated, orrepaired. Furthermore, some of these gel formulations age harden overtime to make reenterability difficult.

In U.S. Pat. No. 4,355,130, a polyalphaolefin extended polyurethane isdisclosed which resolves the stress cracking problem. Suchpolyalphaolefin extended polyurethanes comprise specific polyurethanes,a specific polyalphaolefin extender, and, for reclamation andencapsulation purposes, specific ester coupling agents. The couplingagent is required to compatibilize the formulation so that there will beno "spewing" of extender from the cured material.

DISCLOSURE OF THE INVENTION

It is, therefore, an object of the present invention to provide anextended polyurethane gel system having improved compatibility withcable greases. These compositions also have utility as cable reclamationcompounds and fiber-optic splice encapsulations for thetelecommunications industry.

It is a further object to provide polyurethane gel formulations whichare defined in accordance with specific end use applications.

It has now been found that by utilizing the plasticizers of the presentinvention as the extending agents for polyurethane gels, the resultingsystems are well suited for a number of end use applications includingelectric or telecommunication cable reclamation and encapsulation or asgeneral polyurethane elastomers. Such plasticized polyurethane gelsgenerally comprise a specified polyurethane component and a plasticizercompound having a total solubility parameter of between about 8.3 and8.9 or between about 9.1 and 9.7.

The polyurethane gels of the present invention are characterized ashaving excellent compatibility of the components, a broad viscosityrange, good electrical properties, and the absence of cracking orstressing tendencies on polycarbonate connectors. It is particularly inthe area of compatibility of the components and the electricalproperties of the compositions that these polyurethanes exhibitsignificant improvements over prior art mineral oil extended systems.

When used in the area of reclamation and encapsulation, theseplasticized polyurethane gels provide excellent performancecharacteristics. They possess the low viscosities necessary for initialintroduction into the cable and the ability to retain these lowviscosities for a period of time sufficient to enable them to fill thelength of the free spaces in the cable or form a completelyencapsulating cover. They also possess the ability to displace and/orrepel fluid contaminants and cure in place to form a gel-like urethanestructure which neither spews forth nor exudes the plasticizer. This gelstructure has sufficient rigidity to provide an excellent protectivebarrier, yet can be readily cut and removed if re-entry is desired. Thepolyurethane gels are non-corrosive to copper wire and compatible withthe conventionally used polycarbonate connectors and other polymericmaterials utilized in cable manufacture. The system is also convenientto handle and apply in the field.

The polyurethane which is used in these formulations is generallyprepared by reacting approximately stoichiometric amounts of anisocyanate compound with a polyol. The plasticizer can be added toeither component before they are reacted.

In a preferred embodiment, the isocyanate component is a polyisocyanateprepolymer which is in turn prepared by reacting an excess of anisocyanate compound with a polyol in a manner well known in the art. Aportion of the plasticizer is added to the polyisocyanate prepolymer,and the mixture is then reacted with a polyol containing the remainingportion of the plasticizer to form the gels.

The isocyanate compounds of the invention which can be used for thepreparation of the polyisocyanate prepolymer or direct reaction with thepolyol to form the polyurethane contemplate any organic polyisocyanatehaving 2 or more NCO groups per molecule and no other substituentscapable of reacting with the hydroxyl groups of the polyol. This wouldinclude aliphatic polyisocyanates, cycloaliphatic polyisocyanates, oraromatic polyisocyanates. Typical of such polyisocyanate compounds are3-isocyanatomethyl-3,5,5-trimethyl-cyclohexyl isocyanate (IPDI), toluenediisocyanate (TDI), 4,4' diphenylmethanediisocyanate (MDI),polymethylene polyphenylisocyanate, 1,5 naphthalene diisocyanate,phenylene diisocyanates, 4,4'-methylene bis-(cyclohexylisocyanate),hexamethylene diisocyanate, biuret of hexamethylene diisocyanate,2,2,4-trimethylhexamethylene diisocyanate and combinations thereof, aswell as related aromatic, aliphatic, and cycloaliphatic polyisocyanateswhich may be substituted with other organic or inorganic groups that donot adversely affect the course of the reaction.

The term "aliphatic", as used herein, includes those carbon chains whichare substantially non-aromatic in nature. They may be saturated orunsaturated, unbranched, branched, or cyclic in configuration and maycontain substituents which do not adversely affect migration. Suchaliphatic isocyanates generally have an equivalent weight of from 60 to160 and a viscosity of 1 to 1500 centipoises at 25° C. Exemplary of theliquid long chain aliphatic polyisocyanates are dodecyl diisocyanate,tridecyl diisocyanate, and the like. Polymethylene polyphenyl isocyanateis commercially available from Mobay Chemicals under the trademarkMondur MRS. Two preferred compounds, Mondur MRS and MRS-10, aredark-brown liquids having a slight aromatic ordor. Specifically MondurMRS has an NCO content of 31.5%, an amine equivalent of 133, a viscosityof 200 mPa-s at 25° C., and a density of 1.24 g/cc, while Mondur MRS-10has an NCO content of 31.9%, an amine equivalent of 132, a viscosity of80 mPa-s at 25° C. and a density of approximately 1.24 g/cc. Diphenylenemethane diisocyanates are commercially available in a stabilized liquidform from Upjohn under the trademark Isonate 143L or from Mobay underthe trademark Mondur CD. Specifically, Isonate 143-L is a light yellow,modified diphenyl-methane diisocyanate having an NCO content of 29.2weight percent, an isocyanate equivalency of 144, an acidity value ofless than 0.030 and a viscosity of 35 cps at 25° C., while Mondur CD isa light-yellow modified 4,4' diphenylmethane diisocyanate having an NCOcontent of 29.3 weight percent and a viscosity of less than 100 mPa-s at25° C. Various polyarylene polyisocyanates are commercially availablefrom Upjohn under the trademark PAPI, of which PAPI 94 is typical. PAPI94 is a polymeric methylene diisocyanate containing approximately 98% of4,4' isomer with the remaining 2% being the 2,4' isomer. PAPI 94 has anNCO content of approximately 2.

Suitable polyols for reaction with the organic polyisocyanates includecastor oil, polyether polyols, polyester polyols, hydroxyl bearinghomopolymers of dienes, hydroxyl bearing copolymers of dienes, aminebased polyols, polymeric polyols, and combinations thereof. Such polyolsgenerally have an equivalent weight of from 30 to 6000 and a viscosityof from 1 to 20,000 centipoises at 25° to 60° C. The higher equivalentweight materials, i.e., those having equivalent weights above about 250,are generally preferred.

One polyol which may be used in the preparation of these plasticizedpolyurethane gels is castor oil, a compound primarily composed ofricinolein, which is a glyceride of ricinoleic acid. A typical castoroil comprises a mixture of about 70% pure glyceryl triricinoleate andabout 30% glyceryl diricinoleate-monoleate or monolinoleate and isavailable from CasChem, Inc. as DB Oil.

Suitable polyether polyols include aliphatic alkylene glycol polymershaving an alkylene unit composed of at least two carbon atoms. Thesealiphatic alkylene glycol polymers are exemplified by polyoxypropyleneglycol and polytetramethylene ether glycol. Also, trifunctionalcompounds exemplified by the reaction product of trimethylol propane andpropylene oxide may be employed. A typical polyether polyol is availablefrom Union Carbide under the designation Niax PPG-425. Specifically,Niax PPG-425, a copolymer of a conventional polyol and a vinyl monomer,has an average hydroxyl number of 263, an acid number of 0.05, and aviscosity of 80 centistokes at 25° C.

The general term polyether polyols also includes polymers which areoften referred to as amine based polyols or polymeric polyols. Typicalamine based polyols include sucrose-amine polyols such as Niax BDE-400or FAF-529 or amine polyols such as Niax LA-475 or LA-700, all of whichare available from Union Carbide. As one skilled in the art would know,there are no free amino hydrogens in any of these compounds.

The hydroxyl bearing homopolymers of dienes or hydroxyl bearingcopolymers of dienes are prepared from dienes which includeunsubstituted, 2-substituted or 2,3-disubstituted 1,3-dienes of up toabout 12 carbon atoms. Preferably, the diene has up to about 6 carbonatoms and the substituents in the 2- and/or 3-position may be hydrogen,alkyl groups having about 1 to about 4 carbon atoms, substituted aryl,unsubstituted aryl, halogen, and the like. Typical of such dienes are1,3-butadiene, isoprene, chloroprene, 2-cyano-1,3-butadiene,2,3-dimethyl-1,2-butadiene, and the like. The preferred dienes are1,3-butadiene and isoprene. A hydroxyl terminated polybutadiene isavailable from ARCO Chemicals under the designation Poly-BD R-45HT.Specifically, Poly-BD R-45HT has a molecular weight of about 2800, adegree of polymerization of 50, a hydroxyl functionality of about 2.4 to2.6, a hydroxyl number of 46.6, a hydroxyl value of 0.83, and an iodinenumber of 398.

A wide variety of aromatic and aliphatic diamines may form part of theamine-based polyols, such as N,N-bis(2-hydroxypropyl)aniline andN,N,N',N'-tetrakis(2-hydroxypropyl)ethylenediamine. A typicalamine-based polyol is available from Upjohn under the designation Isonol100, an amber colored liquid polyol having a molecular weight of 209, ahydroxyl number of 534, an equivalent weight of 104.5, an averagefuntionality of 2.0 and a viscosity of 1450 at 50° C. A typicalaliphatic amine-based polyol is available from BASF under thedesignation Quadrol, a viscous liquid polyol with four hydroxyl groups,two tertiary nitrogen atoms, a hydroxyl number of 770 and a viscosity of53,000 cps at 25° C.

Polymeric polyols can be described as conventional polyols with a stabledispersion of vinyl polymers. For example, U.S. Pat. No. 4,104,236discloses such polyols with acrylonitrile-styrene polymers; a furthertypical polyol is available from Union Carbide under the designationNiax 24-32. Specifically, Niax 24-32, a copolymer of a conventionalpolyol and a vinyl monomer, has an average hydroxyl number of 32 and aviscosity of 1300 centipoise at 25° C.

The plasticizer compounds which can be used in this invention includeany compound or mixture of compounds having a total solubility parameterof between about 8.3 and 8.9 or between about 9.1 and 9.7. Compoundshaving solubility parameters higher than 9.7 are too volatile for use ingel formulations, while those having solubility parameters less than 8.3are not compatible with the polyurethane reaction product.

Suitable plasticizer components are esters such as the phthalates oradipates having between about 4 and 13 carbon atoms, since thesecompounds possess solubility parameters falling within theabove-described critical ranges. Certain synthetic ricinoleatecompounds, such as glyceryl tri(acetyl ricinoleate) and similarcompounds which have solubility parameters within the above-disclosedranges, are also useful and, in most cases, preferred due to theirgreater compatibility with a wide range of cable fillers or greaseswhich are typically encountered in the reclamation or encapsulation oftelecommunication or electrical cable.

Specific preferred compounds which can be used as plasticizers inaccordance with the invention are listed below in Table I.

                  TABLE I                                                         ______________________________________                                        PLASTICIZER COMPOUNDS                                                         Compound           Solubility Parameter                                       ______________________________________                                        ditridecyl adipate 8.9                                                        diundecyl phthalate                                                                              9.12                                                       diisodecyl phthalate                                                                             9.15                                                       glyceryl tri (acetyl ricinoleate)                                                                9.3                                                        dibutyl phthalate  9.7                                                        ______________________________________                                    

The specific solubility parameter ranges have been determined by weightgain and conductor pull out tests as shown by the examples.Specifically, compounds having a total solubility parameter whichresults in a weight loss or in which a conductor cable can be easilypulled out are not satisfactory for use in this invention.

Also, one or more of the above-identified plasticizers can be used incombination without departing from the teachings of the inventionprovided that the overall solubility remains in the critical range.

The solubility parameters of the plasticizer compounds are determined asdescribed in the article entitled "A Method for Estimating Both theSolubility Parameters and Molar Volumes of Liquids," by R. F. Fedors,POLYMER ENGINEERING SCIENCE, Vol. 14, No. 2, February, 1974, pp. 147-54.This article is expressly incorporated by reference in this application.

As noted in the above-mentioned article, the total solubility parameterfor a liquid at 25° C. can be calculated from equation 28 as follows:##EQU1## wherein ε_(i) and υ_(i) are the additive atomic and groupcontribution for the energy of vaporization and molar volume,respectively. Based upon a vast amount of data on simple liquids, thesecontributions applicable at a temperature of 25° C. have been compiledin Table 5 of the article. Thus, in order to calculate the totalsolubility parameter for any liquid organic compound, all one needs toknow is the chemical structure of the compound. Therefore, the term"total solubility parameter" as used in this application is intended tomean the solubility parameter of the compound at 25° C., which iscalculated from the experimental energy of vaporization and molar volumevalues given in Table 5 of the Fedors article. The values which appearin Table I of this application are the total solubility parameter forthose compounds calculated in the manner previously described.

With respect to the weight change testing, there are different types ofgreases which may be encountered in telecommunication cable. The mostcommon is FLEXGEL cable filler. FLEXGEL is a registered trademark of theWestern Electric Co. Inc. for their cable filling compounds forwaterproofing electrical cable. Other cables may contain petroleum jelly(PJ) or polyethylene modified petroleum jelly (PEPJ). PEPJ is a highermelting point material than PJ. It should be noted that the ricinoleateshave a wider range of compatibility with all types of cable fillers thanthe other plasticizer compounds.

With respect to the use of these plasticizer compounds in theformulations of the present invention, it should be noted that thosecompounds having a solubility parameter between about 9.1 and 9.7provide clear and transparent gels which are preferred for applicationswhere reenterability is of primary importance. Those compounds havingsolubility parameters between about 8.3 and 8.9 do impart a degree ofopaqueness to the resulting gel with the lower values generallyproviding a higher degree of cloudiness or opaqueness in the gel.However, all the polyurethane gels according to this invention are softwith a low tear strength, and these properties are maintained over timeto provide desirable reenterable compounds.

It should further be noted that all the suitable plasticizer componentsaccording to the invention are low viscosity liquids at roomtemperature.

The polyurethane gels of the present invention are generally comprisedof about 10 to 90 parts by weight of polyurethane, and correspondingly,about 90 to 10 parts by weight of plasticizer. If less than 10 parts ofpolyurethane are used, the resulting gel will have essentially no tearstrength at all, while if less than 10 parts of plasticizer is used, theresulting formulation will not provide the improved properties. Apreferred concentration with particular reference to the reclaiming orencapsulating utility comprises about 10 to 50 parts by weight ofpolyurethane reaction product and about 90 to 50 parts by weight ofplasticizer, a more preferred concentration comprises about 30 to 40parts by weight of polyurethane reaction product, about 70 to 60 partsby weight of plasticizer.

If higher solids content grease compatible formulations are desired, therelative proportions would be about 90 to 50 parts by weight ofpolyurethane and about 10 to 50 parts by weight of plasticizer.

In accordance with the plasticized polyurethanes of the presentinvention, finely divided solid fillers which are commonly employed inthe art as either reinforcing or inert fillers may be utilized. The useof such solid fillers applies mainly to non-reenterable polyurethanes.Conventional fillers include carbon black, asphaltenes, silica,silica-alumina, hydrated silica, zinc oxide, magnesium carbonates,clays, talc, and pulverized reclaimed rubber as well as various mineralfillers which are known in the art. Solid fillers may be employed in theamount of up to about 50 weight percent of the polyurethane.

The present formulations are preferably prepared at the application siteby admixing the resin system with the hardener system. Depending on thedesired utility, the resin and hardener are utilized in amounts meetingthe stoichiometric requirements. The resin component comprises thepolyisocyanate or polyurethane prepolymer, and, all or a portion of theplasticizer. The hardener component comprises the polyol, and whereapplicable, the remaining portion of the plasticizer. The catalyst andoptional additives such as fungicides, pigments, anti-oxidants, moisturescavengers, and the like, are generally added to the hardener component.Catalysts are known to those skilled in the art and may comprise, forexample, heavy metals utilized in amounts of about 0.1 weight percent ofthe hardener component.

As noted, the polyurethane gels of the present invention possess thedesired properties for a range of utilities, with primary emphasis onutilities such as reenterable encapsulants and reclamants for insulatedelectrical devices. Initially, these materials are sufficiently fluid tobe introduced into the core of a cable or mold surrounding a portion ofthe cable and to retain their fluidity for a period of time sufficientto fill all the interior free spaces.

The term "reclamation" is used to include the situation wherein thepolyurethane gel compositions of the invention are injected into damagedtelecommunication or electrical cable to displace any fluid contaminantsand restore the cable to its initial condition. As the gel cures, itexpands and displaces the contaminants in the damaged cable.

The term "encapsulation" refers to the use of the polyurethane gels ofthe invention to seal a splice or connection to a cable. In thisarrangement, the electrical connections are made to an existing cable, aclosure of polyethylene or similar material is made around theconnection, and the gel composition is injected into the space betweenthe closure and cable, where it expands and cures to form a moistureresistant seal.

In its reclaiming function, the polyurethane will thus displace theliquid penetrants from the free spaces within the cable. in theencapsulation utility, a sheath of polyethylene or other suitablematerial is placed around a repaired area of the cable. The polyurethaneis then placed within the sheath, which acts as a mold for the finalouter dimensions of the gel. Thereafter, for either application, astable gel forms within a reasonable period of time to provide a sealagainst penetration of water and other fluid materials or contaminants.

Where reenterability is desired, the selected polyurethane provides agel which is sufficiently soft so as to be readily removed. Theinsulating properties of these reenterable encapsulant and reclamantcompositions are highly improved, particularly with regard to thedissipation factor and volume resistivity of the material. Furthermore,there is no exudation of components used and there is excellentcompatibility with materials employed in the cable construction and withpolycarbonate connectors. In addition, the instant plasticizedpolyurethanes can be utilized as hard volume (permanent) encapsulantsand for general polyurethane elastomeric uses.

EXAMPLES

The scope of the invention is further described in connection with thefollowing examples which are set forth for the sole purpose ofillustrating the preferred embodiments of the invention and which arenot to be construed as limiting the scope of the invention in anymanner. In these examples, all parts given are by weight unlessotherwise specified.

EXAMPLE 1

The following formulations illustrate typical plasticizer/polyurethanegel systems of the invention which are intended for use as reenterablereclamants or encapsulants.

    ______________________________________                                         Resin system   A      B        C    D                                        ______________________________________                                        polymethylene polyphenyl                                                                      23.8   23.8     23.8  3.0                                     isocyanate (1)                                                                castor oil (2)   2.3   --        2.3  1.8                                     diundecyl phthalate                                                                           12.9   76.2     --   45.2                                     ditridecyl adipate                                                                            --     --       12.9 --                                       ______________________________________                                        Hardener system E      F        G    H                                        ______________________________________                                        hydroxyl terminated                                                                           32.0   32.0     32.0 13.4                                     polybutadiene (3)                                                             castor oil (2)   2.9    5.8      2.9  1.8                                     diundecyl phthalate                                                                           65.1   62.2     65.1 34.8                                     ______________________________________                                         (1) PAPI 901 from Upjohn                                                      (2) DB Oil from CasChem, Inc.                                                 (3) PolyBD R45HT from Arco Chemicals                                     

The following polyurethane gels were then prepared by mixing ResinSystems A, B, C, and D with Hardener Systems E, F, G, and H,respectively. After curing, each of these formulations were found to besoft, clear gels which are eminently suitable for use in applicationssuch as the reclamation or encapsulation of telecommunication cable,when a reenterable formulation is desirable.

EXAMPLE 2

The following formulations were then prepared by mixing the followingcomponents together and allowing the mixture to cure.

    ______________________________________                                                       I       J      K                                               ______________________________________                                        polymethylene polyphenyl                                                                        5.0      5.5     4.3                                        isocyanate                                                                    castor oil (2)   --        5.3    --                                          hydroxyl terminated                                                                            45.0      29.2   --                                          polybutadiene (3)                                                             ditridecyl adipate                                                                             50.0      --     --                                          diisodecyl phthalate                                                                           --        60.0   65.0                                        polyoxypropylene diol (4)                                                                      --        --     30.7                                        ______________________________________                                         (1) PAPI 901 from Upjohn.                                                     (2) DB Oil from CasChem, Inc.                                                 (3) PolyBD R45HT from Arco Chemicals.                                         (4) PPG2025 from Union Carbide.                                          

These formulations were also found to be soft, clear, gels, which alsowould be suitable for reenterable repair applications.

EXAMPLE 3

The following polymer system was prepared:

    ______________________________________                                        Component                Parts                                                ______________________________________                                        polymethylene polyphenyl isocyanate (1)                                                                13.6                                                 castor oil (2)           13.3                                                 hydroxyl terminated polybutadiene (3)                                                                  73.1                                                 ______________________________________                                         (1) PAPI 901 from Upjohn.                                                     (2) DB Oil from CasChem, Inc.                                                 (3) PolyBD R45HT from Arco Chemicals.                                    

Then, 65 parts of this polymer system was mixed with 35 parts of thefollowing plasticizers to prepare the designated polyurethaneformulations.

    ______________________________________                                        Plasticizer       Formulation                                                 ______________________________________                                        ditridecyl adipate                                                                              L                                                           dioctyl adipate   M                                                           diundecyl phthalate                                                                             N                                                           6:7 mixture of dioctyl                                                                          O                                                           adipate: mineral oil                                                          2:1 mixture of diisodecyl                                                                       P                                                           phthalate: mineral oil                                                        ______________________________________                                    

Dioctyl adipate has a total solubility parameter of 9.05, which isoutside the scope of the invention. Thus it was used in formulation M asa comparative example. The mineral oil extenders of formulations O and Pwere also used to illustrate comparative examples of plasticizermaterials which are outside of the scope of the invention.

To determine the suitability of the above formulations for greasecompatibility, the formulations were cured on FLEXGEL cable filler and,after curing, the weight change of the formulation was measured.Compatible formulations show a weight gain, which indicates that thegrease is taken into the formulation.

Alternately, incompatible formulations show a weight loss whichindicates an exudation or separation of the extender or plasticizer fromthe gel. Test results are shown below in Table 2.

As a further measure of grease compatibility, an electrical conductorwas coated with FLEXGEL cable filler and encapsulated with the aboveformulations. After the formulations cured, the conductor was pulled outof the polyurethane. The force necessary to separate the conductor fromthe polyurethane was measured and is also listed below in Table 2.

                  TABLE 2                                                         ______________________________________                                        Test Results                                                                                            Pull-out Force                                      Formulation  % Weight Change                                                                            (Lbs)                                               ______________________________________                                        L            +0.4         4.5                                                 M            -1.1         4.1                                                 N            +0.6         6.3                                                 O            -5.0         1.8                                                 P            -4.5         2.0                                                 ______________________________________                                    

It is evident from the preceding table that plasticizers having a totalsolubility parameter between about 9.1 and 9.7 or between about 8.3 and8.9 are grease compatible, whereas compounds having other solubilityparameters are not.

EXAMPLE 4

The following formulation was prepared:

    ______________________________________                                        Component               Parts                                                 ______________________________________                                        polymethylene polyphenylisocyanate (1)                                                                4.8                                                   castor oil (2)          4.6                                                   hydroxyl terminated polybutadiene (3)                                                                 25.6                                                  glyceryl tri (acetyl ricinoleate)                                                                     65                                                    ______________________________________                                         (1) PAPI 901 from Upjohn                                                      (2) DB Oil from CasChem, Inc.                                                 (3) PolyBD R45HT from Arco Chemicals                                     

This formulation was then tested for weight change and conductor pulloutas described above. The results were: % Weight change on various cablefillers:

    ______________________________________                                               FLEXGEL +5.5                                                                  PEPJ    +1.6                                                                  PJ      +0.5                                                           ______________________________________                                         Coated Conductor pull out: 7.0 lbs                                       

This shows that the ricinoleate plasticizer imparts the highest degreeof compatibility with a variety of commonly encountered cable fillers orgreases to the formulation. Other ricinoleates having total solubilityparameters within the above disclosed ranges should also performsimilarly.

While it is apparent that the invention herein disclosed is wellcalculated to fulfill the objects above stated, it will be appreciatedthat numerous modifications and embodiments may be devised by thoseskilled in the art, and it is intended that the appended claims coverall such modifications and embodiments as fall within the true spiritand scope of the present invention.

Having thus described our invention, what we claim as new and desire tosecure by Letters Patent is:
 1. A process for providing a fluidimpervious protective seal around an insulated electrical device whichcomprises introducing the components of a polyurethane gel compositioncomprising about 10 to 90 parts by weight of the liquid reaction productof an organic polyisocyanate and a polyol having an equivalent weightabove 250 in the presence of about 90 to 10 parts by weight of an esterplasticizer compound having a total solubility parameter of betweenabout 8.3 and 8.9 or between about 9.1 and 9.7 into a confined spacesurrounding the section of a device to be protected and allowing saidcomposition to cure to a gel.
 2. The process of claim 1 wherein saidisocyanate compound is selected from the group consisting of aliphatic,cycloaliphatic, and aromatic polyisocyanates.
 3. The process of claim 2wherein said isocyanate compound is polymethylene polyphenylisocyanateor methylene diisocyanate.
 4. The process of claim 1 wherein saidorganic polyisocyanate is a polyisocyanate prepolymer prepared byreacting an excess of a polyisocyanate compound with a polyol.
 5. Theprocess of claim 1 wherein said polyol is selected from the groupconsisting of castor oil, polyether polyols, hydroxyl-bearinghomopolymers of dienes, hydroxylbearing copolymers of dienes, aminebased polyols, polymeric polyols, and mixtures thereof.
 6. The processof claim 5 wherein said polyol is a hydroxyl terminated polybutadiene.7. The process of claim 1 wherein said ester plasticizer compound isditridecyl adipate, diundecyl phthalate, diisodecyl phthalate, ordibutyl phthalate.
 8. A process for providing a fluid imperviousprotective seal around an insulated electrical device which comprisesintroducing the components of a polyurethane gel composition comprisingabout 30 to 40 parts by weight of the liquid reaction product of anorganic polyisocyanate compound and a polyol having an equivalent weightabove 250 in the presence of about 70 to 60 parts by weight of an esterplasticizer compound having a total solubility parameter of betweenabout 8.3 and 8.9 or between about 9.1 and 9.7, into a confined spacesurounding the section of a device to be protected and allowing saidcomposition to cure to a gel.
 9. A process for providing a fluidimpervious protective seal around an insulated electrical device whichcomprises introducing the components of a polyurethane gel compositioncomprising about 10 to 50 parts by weight of the liquid reaction productof a polyisocyanate prepolymer and a polyol having an equivalent weightabove 250 in the presence of about 90 to 50 parts by weight of an esterplasticizer compound having a total solubility parameter of betweenabout 8.3 and 8.9 or between about 9.1 and 9.7 into a confined spacesurrounding the section of a device to be protected and allowing saidcomposition to cure to a gel.
 10. A process for providing a fluidimpervious protective seal around an insulated electrical device whichcomprises introducing the components of a polyurethane gel compositioncomprising about 10 to 90 parts by weight of the liquid reaction productof an organic isocyanate compound and a polyol in the presence of about90 to 10 parts by weight of ditridecyl adipate, diundecyl phthalate,diisodecyl phthalate, or dibutyl phthalate into a confined spacesurrounding the section of a device to be protected and allowing saidcomposition to cure to a gel.
 11. The process of claim 1 wherein saidcomposition is used to encapsulate said device.
 12. The process of claim1 wherein said composition is used to reclaim said device.
 13. Theprocess of claim 11 wherein said composition contains 30 to 40 parts byweight of liquid reaction product and 70 to 60 parts by weight of esterplasticizer compound.
 14. The process of claim 12 wherein saidcomposition contains 30 to 40 parts by weight of liquid reaction productand 70 to 60 parts by weight of ester plasticizer compound.
 15. Theprocess of claim 10 wherein the liquid reaction product is present in anamount of between about 50 and 90 parts by weight and the ester ispresent in an amount of between about 50 and 10 parts by weight.
 16. Theprocess of claim 10 wherein the liquid reaction product is present in anamount of between about 30 and 40 parts by weight and the ester ispresent in an amount of between about 70 and 60 parts by weight.
 17. Aninsulated electrical device comprising a plurality of insulated wireconductors and a cured polyurethane gel composition comprising about 10to 90 parts by weight of the liquid reaction product of an organicpolyiscyanate and a polyol having an equivalent weight above 250 in thepresence of about 90 to 10 parts by weight of an ester plasticizercompound having a total solubility parameter of between about 8.3 and8.9 or between about 9.1 and 9.7.
 18. An insulated electrical devicecomprising a plurality of insulated wire conductors and a curedpolyurethane gel composition comprising about 30 to 40 parts by weightof the liquid reaction product of an organic polyisocyanate compound andpolyol having an equivalent weight above 250 in the presence of about 70to 60 parts by weight of an ester plasticizer compound having a totalsolubility parameter between about 8.3 and 8.9 or between about 9.1 and9.7.
 19. An insulated electrical device comprising a plurality ofinsulated wire conductors and a cured polyurethane gel compositioncomprising about 10 to 50 parts by weight of a liquid reaction productof a polyisocyanate prepolymer and a polyol having an equivalent weightabove 250 in the presence of about 90 to 50 parts by weight of an esterplasticizer compound having a total solubility parameter of betweenabout 8.3 and 8.9 or between about 9.1 and 9.7.
 20. An insulatedelectrical device comprising a plurality of insulated wire conductorsand a cured polyurethane gel composition comprising about 10 to 90 partsby weight of the liquid reaction product of an organic isocyanatecompound and a polyol in the presence of about 90 to 10 parts by weightof ditridecyl adipate, diundecyl phthalate, diisodecyl phthalate, ordibutyl phthalate.
 21. The device of claim 20 wherein the liquidreaction product is present in an amount of between about 50 to 90 partsby weight and the ester is present in an amount of between about 50 and10 parts by weight.
 22. The device of claim 20 wherein the liquidreaction product is present in an amount of between about 30 and 40parts by weight and the ester is present in an amount of between about70 and 60 parts by weight.